If $x \boxdot y = 3x-4y$ and $x \triangleright y = 5x+y$, find $(-3 \triangleright -3) \boxdot -6$.
First, find $-3 \triangleright -3$ $ -3 \triangleright -3 = (5)(-3)-3$ $ \hphantom{-3 \triangleright -3} = -18$ Now, find $-18 \boxdot -6$ $ -18 \boxdot -6 = (3)(-18)-(4)(-6)$ $ \hphantom{-18 \boxdot -6} = -30$.